Late Cenomanian oysters from Egypt and Jordan

Accepted Manuscript Late Cenomanian oysters from Egypt and Jordan Fayez Ahmad, Sherif Farouk, Khaled El-Kahtany, Hashem Al-Zubi, Abdullah Diaba PII: DOI: Reference:

S1464-343X(15)00099-0 http://dx.doi.org/10.1016/j.jafrearsci.2015.04.017 AES 2265

To appear in:

African Earth Sciences

Received Date: Revised Date: Accepted Date:

3 July 2014 27 April 2015 30 April 2015

Please cite this article as: Ahmad, F., Farouk, S., El-Kahtany, K., Al-Zubi, H., Diaba, A., Late Cenomanian oysters from Egypt and Jordan, African Earth Sciences (2015), doi: http://dx.doi.org/10.1016/j.jafrearsci.2015.04.017

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Late Cenomanian oysters from Egypt and Jordan

Fayez Ahmad* Sherif Farouk** Khaled El-Kahtany*** Hashem Al- Zubi**** Abdullah Diabat*****

*Department of Earth and Environmental sciences, The Hashemite University, Zarqa 13115, Jordan; e-mail: [email protected]

**Exploration Department, Egyptian Petroleum Research Institute, Nasr City, 11727, Egypt; E-mail: [email protected]

*** Geology Department, Faculty of Science, King Saud University, Riyadh, Saudi Arabia ****Ministry of Energy and Mineral Resources, Amman, Jordan; [email protected] *****Institute of Earth and Environmental Sciences, Al al-Bayt University, Mafraq, Jordan; [email protected] Abstract Late Cenomanian oysters occur in great numbers, wide distribution, usually as original shells, and can be used as guide fossils in northeastern Egypt and Jordan. Six genera including seven species of typical Tethyan palaeobiogeographic affinity have been recorded from two sections, Wadi Al-Atashieh in central Jordan and west Saint Anthony in north eastern Egypt. The oyster assemblages exhibit a similar stratigraphic trend in Egypt and Jordan. As a result, four oyster zones can be recognized in the upper Cenomanian succession i.e., Ceratostreon flabellatum, Ilymatogyra africana, Costagyra olisiponensis, and Pycnodonte (Phygraea) vesicularis vesiculosa. These zones are correlated with the equivalent ammonite zones. Extinction of some species of these oysters toward the Cenomanian/Turonian (C/T) boundary may be linked to the eustatic sea level rise.

Key words: oysters, Cenomanian, taxonomy, Jordan, Egypt.

Introduction Cenomanian successions in Jordan are widely distributed and well exposed. They are characterized by sporadic planktonic micro- and macrofossil assemblages due to their deposition in comparatively shallow environments. Late Cenomanian oysters are highly diverse, abundant and well preserved, and are widely distributed in the Tethys Ocean (Dhondt et al., 1999; Dhondt and Jaillard, 2005). These taxa can be used as excellent guide fossils. Previous studies of this group concentrated on the taxonomy and many of them neglected to discuss its importance for the biostratigraphy of the eastern Tethys (e.g., Malchus, 1990; Aqrabawi, 1993; Ahmad and AlHammad, 2002; Zakhera and Kassab, 2002a; 2002b; Perrilliat et al., 2006; Berndt, 2002; Abdel-Gawad et al.,

2004a; 2004b and 2007; El Qot, 2006; Mekawy, 2007; Hewaidy et al., 2012; Ayoub-Hannaa and Fürsich, 2011). The aim of this study is to demonstrate the biostratigraphic importance of Cenomanian oysters in Jordan and Egypt and to discuss their palaeobiogeographic affinities. Biostratigraphy of the oysters is correlated with that of the ammonites, which have been encountered in the same sections. Oysters and ammonites were collected from two outcrops; west of Saint Anthony at southern Galala, western Gulf of Suez, Egypt (co-ordinates: 28o57’53.5”N, 32o25´45” E) and at Wadi Al-Atashieh, south-eastern Dead Sea, Jordan (31º02’17”N. 35º34’55”E) (Fig. 1).

Geological setting Cenomanian deposits are the products of the first major transgression that occurred during the Cretaceous period in the eastern Tethys. This major Cenomanian transgression covered large parts of the southern margins of the Tethys where predominantly shallow-water platform sediments were deposited during the Cenomanian and Turonian interval (Burdon and Quennell 1959, Wetzel and Morton 1959, Blankenhorn 1914 and Powell, 1989) overlying Aptian–Albian fluvio-marine deposits. The Cretaceous succession at East Saint Anthony section has been classified, from base to top, into a number of formations (Ghorab, 1961; Awad and Abdallah, 1966; Abdallah and Eissa, 1970; Kuss, 1986): Malha (Aptian–Albian), Galala (Cenomanian), Abu Qada (early Turonian), Wata (Turonian), Matulla (Coniacian–Santonian), Gebel Thelmet (late Campanian), and Saint Anthony (Maastrichtian). The Cretaceous rocks are unconformably overlain by the Southern Galala Formation of Paleogene age. In Jordan, the Cretaceous succession has been subdivided into three lithostratigraphic units, which are the Kurnub Group (Berriasian–Albian), the Ajlun Group (Albian–Cenomanian to mid-Coniacian), and the Late Cretaceous–Eocene Belqa Group (Quennell, 1951; Burdon and Quennell, 1959; Powell, 1989; Powell and Moh’d, 2011; Bandel and Salameh, 2014). The groups are separated from each other by regional unconformities as was stated among others by Powell et al. (1996) and Powell and Moh’d (2011).

Lithostratigraphy In Egypt, the Cenomanian is represented by the Galala Formation (Awad and Abdallah, 1966) which attains about 95 m at the west Saint Anthony section. The formation is well exposed and widely distributed forming mainly the foot of the escarpment of the Galala Plateau. The Galala Formation has been subdivided into

three members named, from base to top, Abu Had, Mellaha Sandstone (Ghorab, 1961), and Ekma (Cherif et al., 1989) (Fig. 2): The Abu Had Member is composed of shales intercalated with sandy marl and limestone yielding abundant macrofossils represented by bivalves, gastropods, echinoids and ammonites. Oysters occasionally form concentrations, generally of shallow-water origin. Starting with the lower boundary of the Galala Formation hemiasterid echinoids are very common, with the consistent occurrence of Hemiaster cubicus (Farouk, 2015). The Mellaha Sandstone Member consists of friable sandstone representing a nearshore marine environment with an about 10-m- thick marl intercalation containing Pycnodonte (Phygraea) vesicularis vesiculosa in its middle. The Ekma Member is composed mainly of argillaceous limestone interbedded with marl and shale bands. It is fossiliferous, especially towards the top, containing among others ammonites. The Galala Formation unconformably overlies the fluvial cross-bedded sandstone of the Aptian–Albian Malha Formation. The contact is easily recognized in the field and characterized by a sharp, irregular, erosional surface with paleo-soils, roots, wood trunks and layers with iron oxides. Its upper contact with the Lower Turonian Abu Qada Formation (Ghorab, 1961) is also unconformable. In Jordan, the Cenomanian–Turonian Ajlun Group is represents a shallow-marine platform setting subdivided into intra-platform basins (Kuss et al. 2003). The sediments of the Ajlun Group in Jordan have been deposited on a continental shelf with somewhat undulating surface. It was bordered by the open sea in the North and by land in the south and southeast. It can be classified into the Naur Limestone, Fuheis, Hummar Shuayb, and Wadi As Sir Limestone formations (Powell, 1989) (Fig. 3). Bandel and Salameh (2014) differentiated, near Amman, eight formations. From older to younger these are Rumeimin, Salihi, Suweilih, Naur (these four first formations have, in several studies, been united in the “Naur Limestone”), Fuheis, Hummar, Shuayb and Wadi Sir. Bandel and Salameh (2014), further subdivided these formations into 37 members, which can be recognized and studied in the area of Amman, especially around the Rumeimin area. Altogether they have traditionally been interpreted to compose the Ajlun Group that is dominated by limestones and marls and is overlain by chalks, flint-rich chalks and calcareous siltstone and marls of the Belqa Group (Wetzel and Morton, 1959). The Naur Limestone Formation (Lower Cenomanian) represents the first transgressive phase of the Tethys during the Late Cretaceous, overlying alluvial plain deposits of the Kurnub Group (Powell, 1989). It consists mainly of bedded sandy limestone with few shale intercalations and changes to nodular limestone

interbedded with shale and sandy limestone up-section. An Early Cenomanian age has been assigned to the Naur Limestone Formation by Powell (1989), Khalil (1992), and Shawabekeh (1998), while other authors assigned a Late Albian to Early Cenomanian age to the formation (e.g., Wetzel and Morton, 1959; Burdon and Quennell, 1959; Basha, 1978; Dilley, 1985; Ibrahim, 1993; Berndt, 2002; Schulze et al., 2005; Bandel and Salameh, 2014). Based on the biozonation with the aid of calcareous nannofossil as represented by Schulze et al. (2005), the Naur Limestone Formation lies in CC9 of Albian–Early Cenomanian age. The Fuheis Formation (Upper Cenomanian), forming gentle slopes, consists of grey-green calcareous siltstone, beside nodular limestones rich in oysters which prefer shallow water. The Fuheis Formation is followed unconformably by the cliff-forming Karak Limestone, especially at Wadi Al-Atashieh. It consists of dolomitic limestone, highly bioturbated at the base, with a thickness ranging from 18 m in Wadi Mujib to 10 m in Wadi Al-Atashieh. Neolobites vibrayeanus, abundant Ilymatogyra africana and Costagyra olisiponensis within the Fuheis Formation indicates a Late Cenomanian age (Fig. 3). The Upper Cenomanian Hummar Formation consists of shale and clay interbedded with argillaceous limestone at the base but up-section is dominated by limestones yielding bivalves and the ammonite Vascoceras cauvini of Late Cenomanian age. It attains about 80 m at Wadi El Mujib, and about 60 m at Wadi Al-Atashieh. Powell (1989) assigned a Late Cenomanian to Early Turonian age to the undifferentiated Fuheis, Hummar, and Shuayb formations of the Karak area. The Shuayb Formation (Upper Cenomanian–Lower Turonian) attains about 100 m at Wadi El Mujib, and about 120 m at Wadi Al-Atashieh. In southern Jordan, the Shuayb Formation can be divided into three members: The lower informal member (Late Cenomanian) is composed of marl – shale alternations with a reduced (macrofaunal) faunal content. The middle Walla Limestone Member (ammonite bed) consists of argillaceous limestone and marl. It is characterized by abundant large ammonites and can be considered a marker bed within the Lower Turonian succession of Jordan (Fig. 3). The most important ammonites recorded and identified in the present study are Choffaticeras sinaiticum, Choffaticeras segne and Vascoceras durandi. These ammonites have also been reported from the Ar Rabba area by Khalil (1992), but he assigned them a Cenomanian age. The upper member of the Shuayb Formation at the Wadi Al-Atashieh section consists of ironoxide stained shale intercalated with gypsum beds which represent deposits of hypersaline lagoons. It is interbedded with ferruginous shale at Wadi Al-Atashieh and with limestone with clay at Wadi El Mujib. This member is followed by shallow marine platform carbonates which consist of thick-bedded limestone with chert intercalations (Upper Turonian of Wadi As Sir Limestone Formation; Powell and Moh`d, 2011).

Material and methods The present study is based on the material collected west of Saint Anthony at southern Galala, western Gulf of Suez, Egypt and at Wadi Al-Atashieh, south-eastern Dead Sea, Jordan. Specimens collected in the field were cleaned in the laboratory. Preservation quality of the material is good to medium. The collected material is housed in the collections of the Paleontological laboratory in the Exploration Department, Egyptian Petroleum Research Institute; under the collection number SHEG2014I for the Egyptian specimens and SHJO2014II for the Jordanian specimens. Systematic palaeontology The systematic classification of the six genera and eight species of oysters follows that of Amler et al. (2000). All linear measurements are given in millimeters. Abbreviations used are as follows: L= shell length; H= shell height; T= thickness of articulated shell.

Suborder Ostreina Férussac, 1822 Superfamily Ostreoidea Rafinesque, 1815 Family Gryphaeidae Vialov, 1936 Subfamily Pycnodonteinae Stenzel, 1959 Genus Pycnodonte Fischer de Waldheim, 1835 Pycnodonte (Phygraea) vesicularis vesiculosa (J. Sowerby, 1823) (Pl. 1A-B)

1823 Gryphaea vesiculosa n. sp. – Sowerby, p. 93, pl. 369. 1990 Pycondonte (Phygraea) vesiculosum (Sowerby, 1823) – Malchus, p. 145, pl. 2, figs. 2-7 (with extensive synonymy). 1993 Pycnodonte (Phygraea) vesiculosum (Sowerby, 1823) – Aqrabawi, p. 79, pl. 5, figs 15-16. 1999 Pycnodonte (Phygraea) vesiculosa (Sowerby, 1823) – Seeling and Bengtson, p. 761, fig. 11a–c 2002 Pycondonte (Phygraea) vesiculosum (Sowerby, 1823) – Zakhera and Kassab, pl. 2, fig. 5. 2004b Pycnodonte (Phygraea) vesicularis vesiculosa (Sowerby, 1823) – Abdel-Gawad et al., pl. 6, figs. 6-7. 2006 Pycnodonte (Phygraea) vesicularis vesiculosa (Sowerby, 1823) – El Qot, 38, pl. 5, figs. 10-11; text-fig. 7. 2006 Pycnodonte (Phygraea) vesicularis vesiculosa (Sowerby, 1823) – Wilmsen and Voigt, 22, pl., 4C-G.

2007 Pycnodonte (Phygraea) vesicularis vesiculosa (Sowerby, 1823) – Abdel-Gawad et al., pl. 4, fig. 4. 2007 Pycnodonte (Phygraea) vesiculosa (Sowerby, 1823) – Mekawy, 213, pl. 2, figs. 7-8. 2012 Pycnodonte (Phygraea) vesiculosa (Sowerby, 1823) – Hewaidy et al., pl. 3, fig. 3a-b. 2014 Pycnodonte (Phygraea) vesicularis vesiculosa (Sowerby, 1823) – Ayoub-Hannaa et al., p. 78, pl. 3, figs. 46. Material: 20 well preserved specimens from the Wadi Al-Atashieh section and 38 well preserved specimens from the west Saint Anthony section.

Dimensions (in mm):

H

L

T

SHJO2014 II 1

21.2

19.7

7.9

SHJO2014 II 10

20

14

11

SHJO2014 II 20

20.2

19.5

8

SHEG2014 I 1

20.5

13.5

10

SHEG2014 I 20

21

19

7.5

SHEG2014 I 38

19.5

14.5

9.5

Remarks: Small, suboval shells with concave postero-dorsal margin. Aqrabawi (1993) mentioned that the Jordanian specimens are up to 45 mm high. The present material has very short chomata. The umbo is prominent and raised above hinge line. The studied material coincides with the forms described and figured by Malchus (1990) from the Northern Galala Plateau. This species differs from Pycnodonte vesicularis (Lamarck, 1806) by its smaller size, thinner shell, and in being more tumid. Distribution: Pycnodonte (Phygraea) vesicularis vesiculosa has been recorded from the Aptian?, Albian–Cenomanian of Europe; from Italy (Moroni and Ricco, 1968) England (Woods, 1913) and Spain (Dhondt, 1984). In Africa, the species is known from Egypt (Malchus, 1990 and Hewiady et al., 2012), Morocco (Freneix, 1972), Libya (Abdel-Gawad, 1995), and Tunisia (Pervinquière, 1912), in the Middle East; from Jordan (Aqrabawi, 1993), Syria (Blanckenhorn, 1934), India (Stoliczka, 1871). It is also known from the Middle to Upper Cenomanian of Brazil (Seeling and Bengtson, 1999). The species is a marker for the Late Cenomanian in Jordan, Libya, and Egypt (Fig. 5).

Occurrence in the present study: The species occurs in the lower Shuayb Formation in Jordan and in the Ekma Member in Egypt, both of Late Cenomanian age. . Subfamily Exogyrinae Vyalov, 1936 Tribe Exogyrini Vyalov, 1936 Genus Exogyra Say, 1820 Exogyra conica (J. Sowerby, 1813) (Pl. 1C-D) 1813 Chama conica sp. nov. – J. Sowerby: 69, pl. 26, fig. 3. 2014 Exogyra conica (Sowerby, 1813) – Ayoub-Hannaa et al., p. 79, pl. 3, figs. 7-8 (with extensive synonymy).

Material: 18 well to moderately preserved specimens from the Wadi Al-Atashieh section and 22 well preserved specimens from the west Saint Anthony section.

Dimensions (in mm):

H

L

T

SHJO2014 II 22

13.2

19.7

8.9

SHJO2014 II 25

25

27

18.6

SHJO2014 II 30

20

14

15

SHEO2014 II 38

13

18

8

SHEG2014 I 40

20

22

13.6

SHEG2014 I 47

17

11

12

SHEG2014 I 50

16.2

22.7

11.9

SHEG2014 I 58

27

29

20

Remarks. Exogyra conica is of medium size, oval to exogyriform, and strongly inequilateral. Left valve strongly convex. Prominent umbones spirally incurved posteriorly. Anterior and ventral margins convex. Posterior margin oblique, either straight or slightly concave. Attachment area small. Ligamental area relatively small and narrow. Commarginal growth rugae undulating. With posterior umbonal keel. Exogyra conica, described here for the first time from Jordan, resembles the species as described by Woods (1913) from the Upper Greensand of England. His figures exhibit a great variation in size of shell and attachment area. Ayoub-

Hannaa et al. (2014) distinguished the species from Exogyra haliotoidea by having a smaller attachment area. Abbass (1962) recorded both Exogyra flabellata and Exogyra conica from the same bed and suggested that Exogyra conica is a variety of Ceratostreon flabellatum. However, Ceratostreon flabellatum differs from Exogyra conica by having thick ribs radiating from a medium keel and occasionally bifurcating forming Vshaped ridges. According to Abdel-Gawad and Gameil (2002), E. conica differs also from E. suborbiculata Lamarck, in having a strong and salient keel. In addition, E. suborbiculata is ornamented with radial ribs which extend from the umbo to the ventral margin or are restricted to the umbonal area, whereas E. conica is commonly ornamented with undulating commarginal growth rugae. Distribution: Exogyra conica has been recorded from the Cenomanian of Morocco (Freneix, 1972), Algeria (Coquand, 1869; Amard et al., 1981), Tunisia (Pervinquière, 1912), Syria (Blanckenhorn, 1934), Pitt and Chatham islands (near New Zealand, Boreham, 1959), Spain (Dhondt, 1982), and England (Woods, 1913). In Egypt, it is known from the Cenomanian of El Baharyia Oasis (Western Desert) and Gebel Shabrawit (Eastern Desert) (Fourtau, 1917), Gebel El-Halal (Fawzi, 1963), Gebel El-Fallig (Abdel-Gawad et al., 2004b), Gebel Nezzazat (Abdel-Gawad and Gameil, 2002), Gebel Musabaa Salama (Kassab and Ismael, 1994), and Gebel Tih (Abbass, 1962). According to Freneix (1972), the species ranges from the Albian to the Cenomanian. Occurrence in the present study: This species occurs in Jordan in the Late Cenomanian Fuheis, Hummar and lower Shuayb formations. In Egypt, it has been recorded from the Abu Had Member only.

Genus Costagyra Vialov, 1936Type species: Exogyra olisiponensis Sharpe, 1850. Costagyra olisiponensis (Sharpe, 1850) (Pl. 1E-H)

1850 Exogyra olisiponensis n. sp. – Sharpe, p. 185, figs. 1-2. 1987 Exogyra olisiponensis Sharpe, 1850 – Bandel et al., pl. 2, fig. 3. 1990 Exogyra (Costagyra) olisiponensis (Sharpe, 1850) – Malchus, p. 134, pl. 10, figs. 2-6. non fig. 1 (with extensive synonymy). 1993 Exogyra (Costagyra) olisiponensis (Sharpe, 1850) – Aqrabawi, p. 67, pl. 4, figs. 3–5; pl. 5, figs. 1, 2. 1994 Exogyra (Costagyra) olisiponensis (Sharpe, 1850) – Kassab and Ismail, p. 231, pl. 4, fig. 5. 1999 Costagyra olisiponenis (Sharpe, 1850) – Dhondt et al., pl. 1, figs. 6-7.

1999 Exogyra (Costagyra) olisiponensis (Sharpe, 1850) – Seeling and Bengtson, p. 756, fig. 9a–c 2001 Exogyra (Costagyra) olisiponensis (Sharpe, 1850) – Zakhera, pl. 2, fig. 8. 2006 Costagyra olisiponensis (Sharpe, 1850) – El Qot, 39, pl. 6, figs. 1-4; text-fig. 7c. 2006 Exogyra (Costagyra) olisiponensis (Sharpe, 1850) – Perrilliat et al., 99, figs. 10-11. 2007 Exogyra olisiponensis (Sharpe, 1850) – Mekawy: 215, pl. 2, fig. 10. 2011 Costagyra olisiponensis (Sharpe, 1850) – Ayoub-Hannaa and Fürsich, figs. J1-2. 2012 Exogyra (Costagyra) olisiponensis (Sharpe, 1850) – Hewaidy et al., pl. 3, fig. 4a-b. 2013 Costagyra olisiponensis (Sharpe, 1850) – El-Qot et al., p. 203, pl. 2, figs. 3, 8. 2014 Costagyra olisiponensis (Sharpe, 1850) – Ayoub-Hannaa et al., p. 81, pl., 3, fig. 1, pl. 4, figs. 1-2. Material: Eight well to moderately preserved specimens from the Wadi Al-Atashieh section and 12 moderately preserved specimens from the west Saint Anthony section..

Dimensions (in mm):

H

L

T

SHJO2014 II 62

53.2

41.2

19.1

SHJO2014 II 67

101.5

83.5

59.5

SHJO2014 II 71

72

50.5

40

SHEG2014 I 40

71

55.5

39

SHEG2014 I 42

44.5

33

24

SHEG2014 I 45

155.2

91.6

75.6

Remarks: Shell inequivalve, inequilateral, umbo strongly curved; left valve convex, and having indistinct beak; narrow umbonal area; ornamented with large, spinose to scaly tubercles. The wide variation in the individuals of Costagyra olisiponensis (Sharpe) led many authors to suggest new specific names such as Exogyra oxyntas Seguenza (1882, p. 116, pl. 18, fig. 1) and Ostrea pseudo africana Choffat (1902, p. 39, pl. 6, fig. 14). The present collection contains some individuals identical with the material of Malchus (1990) in having a more rounded outline than the specimens collected from the Cenomanian of Tunisia by Pervinquière (1912). Aqrabawi (1993) described his collection of Exogyra (Costagyra) olisiponensis from the Middle Lower Cenomanian to Lower Turonian of Jordan as oval to round with the anterior side more straight than the posterior one. This means that the Jordanian specimens agree well with those of Malchus (1990).

Distribution: Costagyra olisiponensis has been recorded from the middle Lower Cenomanian to Upper Cenomanian of the Mediterranean Tethys e.g., Jordan (Aqrabawi, 1993), Europe including e.g., Portugal (Choffat, 1901), and Africa e.g., from Egypt (Malchus, 1990), Morocco (Freneix, 1972), Sahara (Collignon, 1971), Tunisia (Pervinquière, 1912), Angola (Soares, 1961), and Nigeria (Barber, 1958). The species has been recorded from Brazil (Seeling and Bengtson, 1999) and from North and South America by Reeside (1929), Dhondt and Jaillard (1997) (Fig. 5).

Occurrence in the present study: The species has been recorded in Jordan from the Fuheis, Hummar, and lower Shuayb formations, while in Egypt, it occurs in the upper part of the Late Cenomanian Abu Had Member.

Genus Ceratostreon Bayle, 1878

Type species: Exogyra spinosa Matheron, 1848

Ceratostreon flabellatum (Goldfuss, 1834) (Pl. 1I)

1833 Exogyra flabellata n. sp. – Goldfuss, p. 38, pl. 87, fig. 6. 1990 Exogyra (Ceratostreon) flabellatum (Goldfuss, 1833) – Malchus, p. 111, pl. 4, figs. 4-11, pl. 5, figs. 1-7 (with extensive synonymy). 1993 Amphidonte (Ceratostreon) flabellatum (Goldfuss, 1833) – Aqrabawi, p. 63, pl. 2, figs 2–5. 1994 Ceratostreon flabellatum (Goldfuss, 1833) – Kassab and Ismail, p. 231, pl. 4, fig. 7. 1998 Amphidonte (Ceratostreon) flabellatum (Goldfuss, 1833) – Hewaidy et al., p. 62, pl. 3, figs. 1-2. 1999 Amphidonte (Ceratostreon) flabellata (Goldfuss, 1833) – Seeling and Bengtson, p. 755, fig. 8a–d. 2001 Ceratostreon flabellatum (Goldfuss, 1833) – Zakhera, pl. 1, figs. 1-2. 2001 Amphidonte (Ceratostreon) flabellatum (Goldfuss, 1833) – Kora et al. pl. 1, fig. 2. 2002 Ceratostreon flabellatum (Goldfuss, 1833) – Abdelhamid and El Qot, p. 269, pl. 2, fig. 3. 2013 Ceratostreon flabellatum (Goldfuss, 1833) – El-Qot et al., p. 204, pl. 2, figs. 9-12. 2014 Ceratostreon flabellatum (Goldfuss, 1833) – Ayoub-Hannaa et al.,p. 82, pl., 4, figs. 3-5, pl., 5, figs.1-3.

Material: 14 well to moderately preserved specimens from the Wadi Al-Atashieh section and 40 well preserved specimens from the west Saint Anthony section.

Dimensions (in mm):

H

L

T

SHJO2014 II 48

65

46.4

25

SHJO2014 II 52

28.7

36.1

12.8

SHJO2014 II 58

55

36.4

15

SHEG2014 I 73

38.7

46.1

22.8

SHEG2014 I 82

60

41.4

21

SHEG2014 I 93

35.7

43.1

19.8

SHEG2014 I 98

57

39

18

SHEG2014 I 112

31

37

13

Remarks: Shell variable in size, shape and ornamentation; shell generally concentric in shape; both valves ornamented with strong radial ribs occasionally bifurcating; lower valve with a median curved keel from which the ribs start. Some of the studied specimens are very close to Amphidonte (Ceratostreon) flabellatum as figured by Kora et al. (2001) in having an ornament, on the anterior flank consisting of regular, curved, equally spaced radial ribs descending from the median keel; they are finer and greater in number than the posterior ones. This ornamentation is very clear in the present specimens. The author therefore agree with Abbass (1962) in considering Exogyra involuta Seguenza (1882) as a junior synonym. Distribution: Ceratostreon flabellatum (Goldfuss, 1834) occurs in the Aptian?, Albian–Cenomanian of Europe (France (d`Orbigny, 1847), Germany; (Goldfuss, 1833), Austria (Coquand, 1869) of the Middle East (Jordan; Aqrabawi, 1993), north-central and southern Africa (Tunisia; Pervinquière, 1912; Morocco; Freneix, 1972) Egypt; Malchus, 1990), and in the lower upper Cenomanian of Brazil (Seeling and Bengtson, 1999). Occurrence in the present study:

According to Aqrabawi (1993) the species is not known outside the

Cenomanian of Jordan. In fact, this species is widely distributed in the upper Naur Limestone, Fuheis, Hummar, and lower Shuayb formations, while in Egypt, it has been recorded throughout the Galala Formation (? Early to Late Cenomanian).

Genus Ilymatogyra Stenzel, 1971 Type species: Exogyra aritina Roemer, 1852. Ilymatogyra africana (Lamarck, 1801) (Pl. 1J-M)

1801 Gryphaea africana n. sp. – Lamarck, p. 399, pl. 198, figs. 5-6. 1987 Exogyra africana (Lamarck, 1801) –Bandel et al., pl. 2, fig. 7. 1990 Ilymatogyra (Afrogyra) africana (Lamarck, 1801) – Malchus, p. 26, pl. 8, figs. 1-4. 1993 Ilymatogyra (Afrogyra) africana (Lamarck, 1801 ) – Aqrabawi, p. 70, pl. 2, figs. 6–11. 1993 Rhynchostreon mermeti (Coquand, 1862) – Aqrabawi, p. 74, pl. 3, figs. 4, 7. 1994 Ilymatogyra africana (Lamarck, 1801) – Kassab and Ismail, p. 230, pl. 4, figs. 4-6. 1999 Ilymatogyra africana (Lamarck, 1801) – Dhondt et al., pl. 1, figs. 1, 2. 1999 Ilymatogyra (Afrogyra) africana (Lamarck, 1801) – Seeling and Bengtson, p. 758, fig. 9d–g 2001 Ilymatogyra (Afrogyra) africana (Lamarck, 1801) – Zakhera, pl. 1, figs. 3-4. 2002 Ilymatogyra africana (Lamarck, 1801) – Abdelhamid and El Qot, p. 269, pl. 3, fig. 3. 2011 Ilymatogyra africana (Lamarck, 1801) – Ayoub-Hannaa and Fürsich, figs. 2a-e. 2014 Ilymatogyra africana (Lamarck, 1801) – Ayoub-Hannaa et al., p. 85, pl., 5, figs. 4-6.

Material: Eighteen well to moderately preserved specimens from the Wadi Al-Atashieh section and 22 well to moderately preserved specimens from the west Saint Anthony section.

Dimensions (in mm):

H

L

T

SHJO2014 II 62

61.5

42.1

23.6

SHJO2014 II 68

35

23

15.7

SHJO2014 II 76

51

31

13

SHEG2014 I 113

61.5

42.1

23.6

SHEG2014 I 122

35

23

15.7

51

31

13

SHEG2014 I 131

Remarks: Shell outline variable; umbo highly twisted, with small attachment area. Aqrabawi (1993) linked the degree of twisting of the umbo to the size of the attachment area; a small attachment area enabled the

construction of a highly curved to helicoidal umbo. Shell lacks radial ribs; ornamentation consists of coarse growth lamellae, which are smoother and wider on the left valve. Right valve kidney-shaped with a depressed umbo. The two varieties of Malchus (1990) between the two varieties of Ilymatogyra africana from Egypt namely: ‘forma typica’ and ‘forma crassa’ were accepted by Berndt (2002) and are accepted also in the present study. Ilymatogyra africana (Lamarck, 1801) can easily be confused with Rhynchostreon mermeti (Coquand, 1862), which differs in having a thick and large shell, high umbonal area, and wide ligament, which occupies the antero-dorsal part of the shell. Distribution: Ilymatogyra africana (Lamarck, 1801) has been documented from the Middle and Upper Cenomanian of southern Europe (Italy; Trevisan, 1937), of North Africa; (Tunisia; Pervinquière, 1912); Algeria; (Coquand, 1862), the Middle East (Jordan; Aqrabawi, 1993; Ahmad and Al-Hammad, 2002; Berndt, 2002), and of Brazil (Seeling and Bengtson, 1999) (Fig. 5). It has been recorded from the Upper Cenomanian of the northern part of the Eastern Desert, Egypt, by different authors such as Malchus (1990), Abd El-Hamid and El Qot (2002), and Kassab and Zakhera (2002). According to El Qot (2006), I. africana is a geographically very widely distributed species and considered diagnostic of the Middle and Upper Cenomanian. Occurrence in the present study: In Jordan, the species occurs in the Fuheis, Hummar, and lower Shuayb formations, while in Egypt, it is found in the upper part of the Upper Cenomanian Abu Had Member.

Genus Rhynchostreon Bayle, 1878 Type species: Rhynchostreon chaperi Bayle, 1878. . Rhynchostreon suborbiculatum (Lamarck, 1801) (Pl. 1N-P) 1801 Gryphaea suborbiculata sp. nov. – Lamarck, 398, pl. 23, figs. 11-13. 1862 Ostrea mermeti n. sp. – Coquand, p.234, pl. 23, figs. 3-5. 1819 Gryphaea columba n. sp. - Lamarck, p. 198. 1822 Gryphaea columba (Lamarck, 1819) – J. Sowerby, p. 113, pl. 363, figs. 1-2. 1871 Exogyra suborbiculata (Lamarck, 1801) –Stoliczka, p. 462, pl. 35, figs. 1-4. 1912 Exogyra columba (Lamarck, 1819) –Pervinquière, p. 180. 1918 Exogyra columba (Lamarck, 1819) –Greco, p. 7, pl. 1, figs. 15-18, pl. 2, figs. 1-4. 1962 Exogyra suborbiculata (Lamarck, 1801) – Abbass, p. 68, pl. 9, figs.7-8.

1987 Rhynchostreon columbum (Lamarck, 1819) – Bandel et al., pl. 2, fig. 4. 1990 Rhynchostreon mermeti (Coquand, 1862) – Malchus, p. 128, pl. 9, figs. 5-21. 1993 Rhynchostreon mermeti (Coquand, 1862) – Aqrabawi, p. 74, pl. 3, figs. 4–12. 1999 Rhynchostreon mermeti (Coquand, 1862) – Dhondt et al., pl. 1, fig. 4. 1999 Rhynchostreon (Rhynchostreon) mermeti (Coquand, 1862) – Seeling and Bengtson, p. 759, fig. 10a- b 2002 Rhynchostreon mermeti (Coquand, 1862) – Abdel-Hamid and El Qot, p. 271, pl. 3, fig. 4. 2002 Pycnodonte (Phygraea) vesiculosum (Sowerby, 1823) – Ahmed and Al-Hammad, fig. 4 (3-6). 2002 Rhynchostreon mermeti (Coquand, 1862) – Kassab and Zakhera, p. 12, fig. 4 (4-5). 2002 Rhynchostreon mermeti (Coquand, 1862) – Zakhera, fig. 4 (1,2,4,5). 2014 Rhynchostreon suborbiculatum (Lamarck, 1801) –Ayoub-Hannaa et al., p. 86, pl. 5, figs. 7-9. Material: 138 well to moderate to preserved specimens from the Wadi Al-Atashieh section and 248 moderately preserved specimens from the west Saint Anthony section.

Dimensions (in mm):

H

L

T

SHJO2014 II 80

41.2

24

22.5

SHJO2014 II 170

38

21

19

SHJO2014 II 200

37

20.2

18.5

SHEG2014 I 140

43

27

25.5

SHEG2014 I 250

36

19

22

SHEG2014 I 290

35

22

21.3

SHEG2014 I 300

36.7

29.6

24.9

SHEG2014 I 340

43.5

25

23

SHEG2014 I 380

32.2

25.4

20.2

Remarks: Shell elongated-oval or oval to nearly subcircular. Left valve cup-like, convex. Rhynchostreon suborbiculatum is easily confused with, Ilymatogyra africana, but differs in having a thick, large shell, high umbonal area, and a wide ligament which occupies the antero-dorsal part of the shell. The great similarities between Rhynchostreon (Rhynchostreon) mermeti, R. suborbiculatum and R. columbum make it difficult to separate these species, especially when dealing with small specimens, as in Sergipe, Brasil. Therefore, many authors consider R. mermeti and R. columbum as synonyms of R. suborbiculatum according to the law of

priority (e.g., Fourtau, 1904; Seeling and Bengtson, 1999; El Qot, 2006; Hannaa, 2011). All the varieties of R. suborbiculatum may be related to the nature of the substrate and to other environmental factors (Ayoub-Hannaa et al., 2011). Distribution: Rhynchostreon suborbiculatum is widely distributed in the Cenomanian–Turonian of the southern Tethys. It is known from southern Europe (southern Italy; Moroni and Ricco, 1968; Portugal; Choffat, 1901), the Middle East; (Jordan; Aqrabawi, 1993), northern Africa (Morocco, Algeria, Egypt, Malchus 1990, Libya, Algeria, Morocco; Freneix, 1972), Tunisia; (Pervinquière, 1912), western and central Africa; (Nigeria; Barber, 1958; Angola; Soares, 1961), and South America; (Peru; (Dhondt and Jaillard, 1997; Brazil; Seeling and Bengtson, 1999). Occurrence in the present study: In Jordan, the species is widely distributed in the upper Naur Limestone, Fuheis, Hummar, and lower Shuayb formations, while in Egypt, it has been recorded throughout the Galala Formation.

Subfamily Liostreinae Malchus, 1990 Genus Curvostrea Vyalov, 1936 Curvostrea rouvillei (Coquand, 1862) (Pl. 1Q-R) 1862 Ostrea Rouvillei n. sp. –Coquand, 232, pl. 22, figs. 8-10. 1869 Ostrea Rouvillei (Coquand, 1862) – Coquand, 89, pl. 21, figs. 3-6; pl. 24, figs. 7-11. ?1869 Ostrea Rediviva sp. nov. – Coquand, 154, pl. 42, figs. 8-11; pl. 54, figs. 18-30. 1918 Liostrea Rouvillei (Coquand, 1862) – Greco, 4 (186), pl. 1 (17), figs. 6-11. 1962 Ostrea (Crassostrea) rouvillei (Coquand, 1862) – Abbass, 74, pl. 11, fig. 8. 1963 Liostrea rouvillei (Coquand, 1862) – Fawzi, 36, pl. 2, fig. 7. 1972 Liostrea rouvillei (Coquand, 1862) – Freneix: 97, text-fig. 10A-D. ?1985 Ostrea cf. rediviva (Coquand, 1862) – Dominik, pl. 13, fig. 7. 1990 Curvostrea rouvillei (Coquand, 1862) – Malchus, 154, pl. 14, figs. 1-7, 16. 1999 Curvostrea rouvillei (Coquand, 1862) – Seeling and Bengtson, 761, fig. 12a-d. 2002 Curvostrea rouvillei (Coquand, 1862) – Abdelhamid and EL Qot, 273, pl. 3, fig. 8; pl. 4, fig.1. 2002 Liostrea rouvillei (Coquand, 1862) – Abdel-Gawad and Gameil, 88, pl. 2, fig. 11. 2006 Curvostrea rouvillei (Coquand, 1862) – EL Qot, 47, pl. 8, figs. 5-6.

2007 Curvostrea rouvillei (Coquand, 1862) – Mekawy, 218, pl. 3, fig. 5. 2013 Curvostrea rouvillei (Coquand, 1862) – El-Qot et al., p. 206, pl. 2, figs.13, pl. 3, figs. 1, 4, 5. 2014 Curvostrea rouvillei (Coquand, 1862) – Ayoub-Hannaa et al., p. 89, pl. 6, figs. 1-2.

Material: Eight well to moderately preserved specimens from the Wadi Al-Atashieh section and 12 moderately preserved specimens from the west Saint Anthony section.

H

L

T

SHJO2014 II 218

55.2

31.2

17.5

SHJO2014 II 220

20

14

23

SHJO2014 II 223

45

22

15.3

SHEG2014 I 389

25

19

26

SHEG2014 I 392

50

27

15.5

SHEG2014 I 394

20.5

15

23.9

Dimensions (in mm):

Remarks: Shell oval to sub-oval, higher than long. Left valve nearly flat to moderately convex. Right valve less convex to slightly concave ventrally with faintly developed growth lines. Umbo small and not very prominent. Many authors (e.g., Fawzi, 1963; Malchus, 1990; EL Qot, 2006) considered Ostrea rediviva Coquand from the Cenomanian of Algeria as a synonym of Curvostrea rouvillei. Distribution: Curvostrea rouvillei was recorded in Morocco from the Albian to Coniacian being abundant in the Cenomanian (Freneix, 1972), Upper Cenomanian of Tunisia (Pervinquière, 1912), Libya (El-Qot et al., 2013), Egypt (Malchus, 1990; Mekawy, 2007), and Brazil (Seeling and Bengtson, 1999). The species has been recorded from the Santonian of Algeria (Coquand, 1862).

Occurrence in the present study: This species is less abundant and recorded for the first time from Jordan in the Fuheis Formation. In Egypt, it has been recorded rarely from the Abu Had Member.

Oyster biostratigraphy

Four oysters zones have been recognized according to the distribution of the taxa described above (Figs. 2-4); Ceratostreon flabellatum, Ilymatogyra africana, Costagyra olisiponensis, and Pycnodonte (Phygraea) vesicularis vesiculosa. In the following paragraphs each oyster biozone is briefly described:

Ceratostreon flabellatum (O1) Zone This zone is the lowest oyster zone recognized in the present study, overlying the barren interval of the Kurnub Group or its lateral equivalent the Malha Formation in Egypt. It is defined as the interval from first occurrence (FO) of Ceratostreon flabellatum to the FO of Ilymatogyra africana. Macrofossils are rare, moderately preserved, and of low diversity without any ammonite record in the basal part of the Naur Limestone Formation. The zonal species Ceratostreon flabellatum has a wide stratigraphic range, from the Albian to Senonian according to Freneix (1972) and Freneix and Viaud (1986), and from the Aptian? to Cenomanian according to Malchus (1990), Aqrabawi (1993), and Seeling and Bengtson (1999). In Sinai, the lowest occurrence (LO) is of Late Albian age, based on its position below the basal Cenomanian Orbitolina conica Zone (Abdel-Gawad et al., 2004a). This zone is thought by different authors in Egypt to be of? Early–Middle Cenomanian age (e.g., Khalil and Mashaly, 2004; Abdel-Gawad et al., 2006). It is also coeval to the upper part of the Hemiaster cubicus Zone of Kora et al. (1993) which described from Lower Cenomanian sediments of Sinai and Middle Cenomanian rocks of the Galala plateaux, Egypt.

Ilymatogyra africana (O2) Zone This zone is defined as the interval from FO of Ilymatogyra africana to LO of Costagyra olisiponensis. Oysters are highly abundant and quite diverse in this zone including Ceratostreon flabellatum, Rhynchostreon suborbiculatum, Ilymatogyra africana, which represent a good marker of the Cenomanian. This zone has been recorded from the Cenomanian of Egypt, Algeria, Tunisia, Libya, Italy, Israel and Morocco (Fawzi, 1963; Bandel et al., 1987). The presence of Neolobites vibrayeanus in this oyster zone indicates a Late Cenomanian age (Fig. 4). N. vibrayeanus is widespread, but is particularly well documented from the Tethyan Realm of northern and central Africa and the Middle East in shallow subtidal environment (e.g., Lefranc, 1981; Lewy et al., 1984; Wiese and Schulze, 2005).

Costagyra olisiponensis (O3) Zone

This zone is ranges from the FO of Costagyra olisiponensis to FO of Pycnodonte (Phygraea) vesicularis vesiculosa. The zone has been recorded in the Fuheis Formation or upper part of the Abu Had Member. The rich assemblage of bivalves in this zone includes Costagyra olisiponensis, Ceratostreon flabellatum, Rhynchostreon suborbiculatum, Ilymatogyra africana, Exogyra conica, and Gyrostrea deletteri. The Costagyra olisiponensis species is a good marker for the Upper Cenomanian in Egypt, Jordan, and Libya (Greco, 1918; Abbass, 1962; Fawzi, 1963; Bandel et al., 1987; Kuss and Malchus, 1989; Hewaidy et al., 2012; El-Qot et al., 2013).

Pycnodonte (Phygraea) vesicularis vesiculosa Zone (O4) This is the latest Cenomanian zone based on oysters in the present study. It is defined as the total range of the nominal taxon. The oyster diversity is decreasing in this zone, associated taxa being Costagyra olisiponensis, Ceratostreon flabellatum, Rhynchostreon suborbiculatum, Rhynchostreon columba, and R. mermeti. Pycnodonte vesiculosum has been recorded previously from the Upper Cenomanian of Tunisia, Algeria, France, Italy, India, and Israel (Pervinquière, 1912; Fawzi, 1963; Greco, 1918; Stoliczka, 1871). The oyster Pycnodonte (Phygraea) vesicularis vesiculosa Zone is widely distributed during the late Cenomanian (Malchus, 1990). Its range is approximately equivalent to that of the ammonite Vascoceras cauvini Zone (Kora and Hammama 1987; Abdel Gawad, 1999; Kassab and Obaidalla, 2001; Hewaidy et al., 2012; Farouk, 2015). This zone is documented in the upper part of the Galala Formation in Egypt and the Hummar Formation in Jordan (Fig. 4).

Cenomanian-Turonian (C/T) boundary Across the C/T boundary a significant faunal change, documented by the disappearance or extinction of some oysters, can be observed, occurring during a peak global greenhouse interval, attributed to a maximum sea level rise (Dhondt 1981; Aqrabawi 1993; Berndt, 2002; Powell and Moh’d 2011). The transition from Cenomanian to Turonian in Jordan is connected to a horizon at the base of the Wadi Sir Limestone that indicates reworking and a gap in sedimentation (Bandel and Salameh 2014). In the present study, the Cenomanian/Turonian boundary is placed within the Shuayb Formation directly above the extinction of Cenomanian oysters. It is marked by a facies change from a thick limestone rich in Cenomanian oysters to mainly barren shale followed by argillaceous limestone with abundant large-sized Turonian ammonites of the Walla Limestone Member, which are characterized by a rich assemblages of large lower Turonian ammonites (e.g. Choffaticeras segne (Solger), Ch. securiforme (Eck), Ch. quaasi (Peron), Kamerunoceras turoniense (d’Orbigny), Mammites nodosoides (Schlothein), Vascoceras rumeaui (Collignon), Neoptychites cephalotus (Courtiller) and Thomasites rollandi

(Thomas and Peron), In Egypt, a similar sharp faunal change takes place at the base of Vascoceras proprium Zone accompanied by a sudden lithological change reflecting a marked transgression occurring at the Cenomanian-Turonian boundary (Hewaidy et al., 2012 ; Farouk, 2015). This change in faunal and lithological content corresponds to a sequence boundary KTu1; 93.8 Ma recorded from northern Europe and India (Gale et al., 2002; Haq 2014) and also observed in many parts of Egypt and the Negev (Bauer et al. 2003; Farouk, 2015). The timing of the interruption in deposition and connected changes in the macrofauna coincides with the wellknown Oceanic Anoxic Event (OAE2) which shows a conspicuous positive δ13C excursion (Sepùlveda et al., 2009; Wendler et al., 2014). Dhondt (1981) related the increase in the diversity of oysters in the Cenomanian to the major transgression that took place at the beginning of the stage. She related the decrease in number of species in the Turonian compared to the Cenomanian to the relative short duration of this interval and to sudden changes in facies. Exogyrine oysters, such as the genera Ceratostreon, Ilymatogyra, Exogyra, Pycnodonte and Rhynchostreon, preferred shallow waters, i.e. preferred mid-shelf environments (25-50 m) in depth (Dhondt et al. 1999). The cause of their extinction remains unresolved despite the many hypotheses that have been proposed. Most of them have focused on global physical environmental changes (Fischer and Bottjer, 1995; Macleod and Huber, 1996). These environmental changes are mainly linked with the eustatic sea level rise characteristic of this period, together with high planktonic activity, anoxic or hypoxic waters, and detritus input. Oysters where one of the major group affected by the C‒T crisis. As result of the Cenomanian-Turonian transgression, conditions became too deep for oysters to flourish, similarly to the case of the Turonian oysters of North Africa (Dhondt et al. 1999) and Brazil (Seeling and Bengston 1999). Palaeobiogeographic notes During the Cenomanian, northern Egypt and Jordan were part of the broad northern shelf of the Arabian-African carbonate platform, which extended from Morocco to Oman along the southern margin of the Tethyan Ocean (Philip and Floquet 2000). The first major marine transgression in the study area took place during the Cenomanian, documented by the deposition of shallow marine sediments overlying the Aptian/Albain fluviomarine deposits in northern Egypt and Jordan. In the Cenomanian time, a mixed shallow marine siliciclastic carbonate ramp, rich in oysters was established in the study areas. Oysters occasionally formed concentrations in shallow-marine environments of the shelf seas of the southern Tethys during this interval (Fig. 5). In this shallow sea locally oysters found good living conditions and as a result their shells accumulated. These oysters have a wide geographic distribution and can help in reconstructing of the paleogeographic setting during the

Cenomanian time. Since they do not differ from those growing in other parts of the shallow parts of the Tethys Ocean these oysters represent good indicators for stratigraphy and for the interpretation of the environment. The Cenomanian oysters of Jordan are dominated by genera of the subfamily Exogyrinae (Ceratostreon, Exogyra, Ilymatogyra and Rhynchostreon). These taxa have a wide Tethyan distribution and have been described also from Cenomanian strata of North and South America. Their occurrence in central Asia indicates that they had a good dispersal potential (Dhondt et al. 1999; Dhondt and Jaillard, 2005). Most of the oysters from Jordan grew to a large size. Taphonomic data (e.g., little or no fragmentation, equal number of right and left valves) suggest that the majority of these oysters accumulated in situ and were not transported. The latter would have destroyed or selectively removed the lighter, more fragile right valves (Feldmann and Palubniak, 1975). The paleogeographic distribution of the reported oysters has a strong Tethyan affinity which strongly resembles that of other Tethyan regions in the eastern Mediterranean region including (Lebanon, Palestine), northern and northwestern Africa (Libya, Tunisia, Algeria, Morocco), western and central Africa (Angola, Niger), and southern Europe (Portugal, Spain, southern France, Sicily). The marine connection between the Tethyan regions and West Africa via the (the) Trans-Sahara epicontinental sea during the Cenomanian-Turonian is documented by the presence of high proportions of the identified fauna over large areas in West Africa (Dhondt et al. 1999; Kora et al., 2001). Conclusions The Cenomanian oysters from Egypt and Jordan have shows a similar stratigraphic distribution and may be used as guide fossils in shallow-marine environments. Many oysters form layers in either of the two sections studied indicating that ecological conditions were similar during deposition. These were open marine, shallow environment with well oxygenated water. Four oyster biozones according to their vertical distribution are recognized: Ceratostreon flabellatum (O1), Ilymatogyra africana (O2), Costagyra olisiponensis (O3), and Pycnodonte (Phygraea) vesicularis vesiculosa (O4) in ascending order. Zone O1 is nearly barren of ammonites; zones O2 and O3 are equivalent to the zone formed by the Neolobites vibrayeanus Zone that defines the Late Cenomanian; while the Zone O4 falls within the Vascoceras cauvini ammonite Zone of latest Cenomanian age. The well documented change of species and genera of shallow-marine oysters near the Cenomainan‒Turonian boundary may be related to global sea-level rise. Possibly, paleoecological conditions changed when the paleoenvironments deepened which is indicated by large ammonite assemblages during the early Turonian transgression. The identified oysters exhibit a strong affinity to the Mediterranean province of the Tethyan realm.

Acknowledgments Special thanks to Prof. Franz Fürsich, and Prof. Klaus Bandel for fruitful discussion and careful revision of the manuscript.

References

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Fig. 1 Landsat image showing the location of the studied sections (source from Google Earth).

Fig. 2. Stratigraphic distribution of ammonites and oysters in the west Saint Anthony section, Egypt. A= Ammonit zones (A1= Thomalites sp., A2= Neolobites vibrayeanus, A3= Vascoceras cauvini, A4, Vascoceras proprium, A5= Choffaticeras segne) O= oyster zones (O1= Ceratostreon flabellatum, O2= Ilymatogyra africana, O3= Costagyra olisiponensis, O4= Pycnodonte (Phygraea) vesicularis vesiculosa).

Fig. 3. Stratigraphic distribution of ammonites and oysters in Wadi Al-Atashieh, Jordan. For key of symbols see Fig. 3.

Fig. 4. Stratigraphic distribution of Cenomanian oysters in southern Jordan plotted against the recorded ammonite zonation and bioevents.

Fig. 5. Palaeogeographic map showing the distribution of Ilymatogyra africana, Costagyra olisiponensis, and Rhynchostreon suborbiculatum in the late Cenomanian (after Dhondt, 1992; Malchus, 1996; Dhondt et al., 1999). Palaeogeographic map after cpgeosystem.com.

Figs. A-B. Pycnodonte (Phygraea) vesicularis vesiculosa (J. Sowerby, 1823). Upper Cenomanian, Shuayb Formation, Wadi Al-Atashieh section, sample 35. Figs. C-D. Exogyra conica (J. Sowerby, 1813). Upper Cenomanian, Fuheis Formation, Wadi Al-Atashieh section, sample 19. Figs. E-H. Costagyra olisiponensis (Sharpe, 1850). Upper Cenomanian, Shuayb Formation, Wadi Al-Atashieh section, sample 20. Fig. I. Ceratostreon flabellatum (Goldfuss, 1833). Upper Cenomanian, Abu Had Member, west Saint Anthony section, sample 6. Figs. J-M. Ilymatogyra africana (Lamarck, 1801) forma crassa. Upper Cenomanian, Fuheis Formation, Wadi Al-Atashieh section, sample 19. Figs. N-P. Rhynchostreon suborbiculatum (Lamarck, 1801). Upper Cenomanian, Abu Had Member, west Saint Anthony section, sample 6. Figs. Q-R. Curvostrea rouvillei (Coquand, 1862). Upper Cenomanian, Abu Had Member, west Saint Anthony section, sample 10.



Seven Late Cenomanian oysters are recorded from Egypt and Jordan.



The oyster assemblages exhibit a similar stratigraphic trend in Egypt and Jordan.



Four oyster zones can be recognized.

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These zones are correlated with the equivalent ammonite zones.



The recorded oyster assemblages of typical Tethyan palaeobiogeographic affinity.